7/23/2019 A 168297

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DEPARTMENT

OF THE

ARMY

Office

of

the Chief

of

Engineers

Washington, D.C. 20314

IN

DAEN-ZCF-U

Technical Note

No.

86-3

~ ci

FACILITIES

ENGINEERING

LUN

4 8

Maintenance

and Repair

J

Q

USE

OF DIETHYLAMINOETHANOL,

MORPHOLINE,

AND

CYCLOHEXYLAMINE

FOR

CONDENSATE

RETURN LINE

CORROSION

PREVENTION

1.

Purpose. This

technical

note provides

a

description

of

and direction

for

use of three

chemicals: diethylaminoethanol LEAE),

morpholine,

and

cyclohexylamine.

These chemicals

are

used

-in Army boiler

plants to prevent

internal

corrosion of condensate

return

lines.

2.

Applicability. This

technical

note

applies

to

all facilities

engineering

elements

responsible for

the operation

and

maintenance

of steam

generating

boiler

systems.

3.

General.

Replacement

costs

for underground

steam/condensate

systems

are

high.

There is

also a high cost associated

with reduced efficiency

while

systems are

corroding.

The use

of

neutralizing

amines,

notably DEAE,

morpholine,

and cyclohexylamine,

play

a large

role

in the

curtailment

of

condensate

corrosion.

This

note

describes the

use

and

properties

of

these

amines and

provides information

to simplify the choosing

of

an appropriate

neutralizing

amine to

give

the most

economical and effective

results in

different

systems.

4.

Disussion.

r

i oundl~a

I4.

iscussionforublic

release and

sale; its

Thisldocument

s

u

bi ee

ppoe

a.

Condensate Corrosion. s

--

1) Condensate return

line corrosion

prevention

is an important

aspect

of

boiler

water

chemistry. Replacement costs

for

underground

steam/condensate systems

are expensive,

not to mention

the

cost

of the energy

L

in

the

form of

heat

in the condensate

that is

wasted while

the

corroding

J_.-.J

system

is

failing.

Also,

high

makeup

rates,

due

to

loss

of condensate,

often

S I

lead

to

difficulty in maintaining

proper

boiler

water

chemistry. Damage to

the

boilers

themselves from

scale and corrosion

can also occur.

Corrosion

of

Ilt) return

line systems

is

more common

in installations having

extensive

return

systems,

such

as

central energy

plants.

86

0

7/23/2019 A 168297

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DAEN-ZCF-U

Technical

Note

No. 86-

2) Condensate

piping

corrosion

is usually

caused

by

the presence

ot

carbon

dioxide,

oxygen,

or

potable

water

contamination

in

returning

condensate. Oxygen

can

enter

return

lines

through

leaky traps, pumps,

valves,

and fittings

or

with boiler

feedwater

if

not completely

deaerated

and

treated

with

sodium

sulfite.

Pitting

of

return

piping

is

indicative

of

corrosion

caused

by

oxygen

or potable

water

contamination.

Corrosion due

to

oxygen can

be

prevented by properly treating boiler

water and sealing leaks in

the

system.

Corrosion due

to

contamination

can

be prevented by

stopping

leakages

of mineralized

water

into the return system,

generally

through

leaking hot

water

heater

tubes.

3)

Carbon

dioxide

in

condensate

originates

from boiler

makeup

water

alkalinity.

Carbon

dioxide causes

corrosion

in

the

form of grooving

or

channeling

along the

bottom

of the

condensate

return

pipe.

Since

all Army

boiler

plants

use

feedwater

with

at

least

some

alkalinity,

corrosion

due

to

carbon

dioxide

is

a

serious

and common torm

ot

condensate

corrosion.

4)

Carbon

dioxide

is

produced

in

boilers

because

boiler

water

temperatures

cause teedwater alkalinity

in

the form of

bicarbonate to

break

down into hydroxide

and carbo,, dioxide.

HC03

- - - -

eat

- -

>

OH

+ CU

2

bicarbonate

hydroxide carbon

dioxide

(5)

The hydroxide remains

in

the

boiler

water

and

raises

the

causticity

and pH levels.

The carbon

dioxide

is

a gas

and

leaves

the boiler

with

steam,

eventually

dissolving in condensed

steam. Carbon

dioxide

dissolved in water

is acidic,

forming carbonic

acid

as

shown below.

CU

2

+

H

2

0

HZ

C

3

carbon

dioxide

water carbonic

acid

6)

Carbonic

acid, like

any other

acid, is corrosive.

Condensate

corrosion due to carbon

dioxide can

be prevented

by

minimizing the amount of

carbon

dioxide

produced

in the boiler

and

by

treating

the

residual with

neutralizing

amines,

a

family

of

volatile

alkaline

liquids.

(7)

Diethylaminoethanol,

morpholine,

and

cyclohexylamine

are the

three

most

widely

used

neutralizing

amines.

Historically,

only

morpholine

and

cyclohexylamine

have

been

authorized

for use

in Army boiler

plants. Once

carbon

dioxide

is produced

in

the boiler,

its corrosive

ettects can

be

minimized

by

the

addition

of

these

amines

to

neutralize

the

eftect

of

carbon

dioxide

by raising

condensate

pH to

a minimum

ot 7.b.

The amines

are

generally

fed

separately from other chemicals

into the

boiler

steam

drum

and

go over

with steam

and dissolve in the

condensate.

8) Each

ot

these amines

will

not

work

equally

well

in all

systems.

Optimum

results

are

obtained

by

choosing

the appropriate

amine on a system

by

system basis. The

following

is a description

of

UEAE,

then morpholine

and

cyclohexylamlne

and

finally

a

neutralizing amine

selection

chart.

7/23/2019 A 168297

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DAEN-ZCF-U

Technical

Note

No.

86-

b.

Diethylaminoethanol.

(1)

Diethylaminoethanol

(DEAE)

is

a

currently

available

and

widely

used

amine.

DEAE has

a

vapor-liquid

distribution

of

1.7. This

is equivalent

to

1.7

parts

in

steam

to

every

one

part

in

condensate. This

means that

UEAE

will have

a

relatively

uniform

distribution

throughout

return

condensate.

This

makes

DEAE

ideal

for

the

protection

of

moderate

length

systems

in between

the

range

of

either

morpholine

or

cyclohexylamine

used

separately.

The

boiling

point

of DEAE

is

3 b

OF

but it

forms

an azeotrope

a

liquid

mixture

having

a

constant

minimum

boiling

point)

with

water

to

boil

at 21U

OF

thus

enabling

DEAE

to be used

in

low

pressure

systems,

especially

those

having

high

feedwater

bicarbonate

and

carbonate

alkalinity.

Morpholine

is

not suitable

for

low

pressure

systems

because

of

its

high

boiling

point

and

cyclohexylamine

may

cause

problems

in

systems

with

high

teedwater

alkalinity

(above

7b

ppm).

2)

High feedwater

alkalinity

produces

a high level of

carbon

dioxide

equiring

large

dosages

of amines.

The

solubility

of

amines

and

carbon

dioxide

together

is

limited. They

form

bicarbonate

salts,

the

least

soluble

of

which

is

cyclohexylamine

bicarbonate.

When

carbon

dioxide

and

cyclohexylamine

are

present

in

high amounts,

cyclohexylamine

bicarbonate

deposits

out.

The

likely

area

for formation

of

deposits

is

in

low flow

areas

at the

far

end

of the

return

system.

This problem

can

be

avoided

by reducing

feedwater

alkalinity

(dealkalization)

or

by

using

DEAE

in place

of

cyclohexylamine

in

systems

with

high

feedwater

alkalinity.

c.

Morpholine.

Morpholine

has

a low

vapor-liquid

distribution

ratio

of

0.4.

This

is

equivalent

to

U.4

part

in

the steam

to

1.U

part

in condensate.

Since

more

morpholine

tends

to

be

present

in

the

liquid

phase

(condensate),

it

*

will

drop

out

of

steam

early

making

it

suitable

for

protection

of

short

to

moderate

length

condensate

return

systems.

However,

since

the

boiling

point

of

morpholine

is

264

OF,

it

can

only

be used

in

high

pressure

systems,

at

least

lb psig but

best

above

5b

psig.

Because

of

its

high

boiling

point,

very

little

morpholine

is

lost

in deaerators

from

returning

condensate.

d.

Cyclohexylamine.

Cyclohexylamine

has

a

high

vapor-liquid

distribution

ratio

ot

4.7.

It

is best

suited

tor

protection

ot

the

far reaches

ot

long

systems.

In

very

long

systems,

it is

necessary

to also

treat

with

morpholine

to

protect

parts

ot

the system

close

to

the

boiler.

Cyclohexylamine

boils

at

73 OF

but

forms

an

azeotrope

with

water

to

boil

at

2U5

OF

Thus

it can

be

used

in

low

pressure

steam

systems.

Cyclohexylamine

also

provides

good

protection

in systems

without

deaerators.

However,

cyclohexylamine

should

not

be used

in

systems

with a

feedwater

bicarbonate

and carbonate

alkalinity

ot Ib

ppm

or

higher,

as

explained

previously.

In addition,

care

should

be

used

when

feedwater

alkalinity

is above

bU

ppm.

e.

Morpholine/Cyclohexylamine.

A mixture

of

morpholine

and

cyclohexylamine

can

also

be used

to

provide

full

protection

in

medium

and

large

systems.

Morpholine

will

protect

the

near

ends

of

the

system

and

cyClohexylamine

will

protect

the

tar

sections.

The

optimum

ratio

ot each

amine

in the

mixture

is

determined

by

performing

condensate

pH

surveys.

Une

can

start

with

a

mixture

ratio

ot I

part

cyclohexylamine

to

3

parts

morpholine

(2b/75

percent).

The

condensate

pH

survey

is then

conducted

by

taking

7/23/2019 A 168297

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DAEN-ZCF-U

Technical

Note

No

86-

condensate

samples

from

representative

locations

in

the return

system.

It

samples

from far sections

have a

lower pH

than

other

samples,

increase

the

amount of

cyclohexylamine

in

the

mixture

and vice-versa.

Another pH

survey

should

be conducted

whenever

the

ratio

is changed. Eventually,

samples

taken

from

points

throughout

the

system should

be

within

the

optimum

pH

range ot

7.b

to 8.0 or

slightly

higher.

f. pH Limits.

The

recommended

pH

limit for condensate

in all

return

systems

is 7.5

to 8.U.

Condensate

pH should

not be

allowed

to

fall below

7.b

anywhere

in a

return

system.

Corrosion

rates increase

rapidly

as pH falls

below 7.h.

In some

systems

the pH may

reach above

8.0

in some

parts of

a

return

system when

maintaining

the minimum

pH

ot 7.b throughout

the

entire

system.

g.

Chemical

Feeding.

Feeding

of neutralizing

amines,

including

DEAE,

is

preferably

done

by

means of

continuous

feed

pumps

to

keep their

concentration

in

the boiler

and

condensate

at

a

fairly constant

level.

They

can

be fed

directly

into the

boiler steam

drum

or

main steam

header.

h.

Handling

and Safety

Measures.

1) Careful

attention

must

be

given to

the handling

of

these

chemicals.

All

neutralizing

amines can

cause

severe

burns and

are irritating

to

eyes, skin,

and mucous

membranes.

In

concentrated

solutions,

they

are

also

very flammable.

Cyclohexylamine

at 98 percent

concentration

is

about as

flammable

as pure alcohol.

When handling

amines,

personnel

will

insure

that

they

wear

rubber

gloves, a

face

shield,

and a rubber

apron.

If any

liquid

gets

on clothes,

the

clothes

will

be changed

immediately.

An emergency

shower

and eye

wash fountain

will

be

available in

the

immediate

area

in case

of

splashing

onto

skin

or

into

eyes.

2)

Amines

can

be

purchased

in

concentrations

of

approximately bU

percent,

or a little

less, to

greatly

decrease

the

hazards

of

handling

these

chemicals.

Cyclohexylamine

and

morpholine

can

be purchased

through

the

Federal Supply

Schedule

for

Boiler

Feedwater

and

Air-Conditioning

Compounds.

Cyclohexylamine

is available

in 6U

percent

and 98 percent

solutions

and

morpholine

is

available

in 4U

percent,

91

percent,

and

98 percent

solutions

through

the schedule.

i. Costs.

The

costs of

these amines

are approximately

the same

on a

weight

basis.

The

costs of

applying

these amines

differ,

however.

In water

containing

1U ppm

of

carbon

dioxide,

it takes

37

ppm ot

morpholine

to

bring

the

pH up to

8.U.

If cyclohexylamine

is

used

instead

of

morpholine,

only

lb

ppm are required

and

it

VE E

is used,

22

ppm are

required.

Even

though

more

morpholine

is

required

to

treat

the

same

amount

ot

carbon

dioxide,

less

morpholine

is

lost through

deaerators

making

the

cost of

treating

with

morpholine

somewhat

lower

than treating

with

DEAE or

cyclohexylamine.

Uverall

treatment

costs associated

with

LE E

and

cyclohexylamine

are

about the same.

4

7/23/2019 A 168297

5/8

DAEN-ZCF-U

Technical Note

No.

86-

PHYSICAL

AND CHEMICAL

PROPERTIES

OF

NEUTRALIZING

AM4INES

DEAE Morpholine

Cyclohexylamine

Boiling

point

3250 F

2640

F

2730

F

100 percent

amine)

Boiling point

2100

F

----

205 F

PAil

ne/water

azeot rope)

Decomposition

Temperature

7940 F

6440

F

6260 F

Vapor/Liquid

1.7 0.4 4.7

Distribution

ratio

Specific

gravity

0.88

1.002

u.86

100 percent

pH,

100

ppm

solution

10.3

9.7

10.7

Amount

of amine

ppm)

22 37 15

required

to

maintain

a

pH of

8.0 in

ater

con-

taining

10

ppm

CO

Accession

For

NTIS

GR I

DTIC TAR

unalo

2.d

iDist

Special

TABLE 1

b

7/23/2019 A 168297

6/8

DAEN-ZCF-U

Technical

Note

No.

86 -

NEUTRALIZING

AMINE SELECTION CHART

Low Pressure

High

Pressure Systems

(above 15

psig)

Amine

(below

15

psi) Short

Dist.

Medium system Long

system

system length

1 mile)**

___________________

7/23/2019 A 168297

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DAEN-ZCF-U

Technical

Note

No.

86-

j. Restrictions.

No

neutralizing

amines

(including

DEAE)

are

authorized

for

use

in steam

supplied

for

direct

contact

cooking

or

humidification

(AR 42U-

49,

paragraph

2-2bb).

A

steam-generating

heat

exchanger

will

be

installed

to

provide

amine-free

steam

at all

such

locations.

k. Tables.

(1) Table

1

lists

the

pertinent

physical

and chemical

properties

of

the

neutralizing

amines.

2)

Table

2 is a

yeneralized

selection

chart to

aid in

choosing

the

proper

amine

tor various

boiler

plant

systems.

5.

Conclusions.

The

use of

neutralizing

amines

is

an important

part of

good

boiler

water

treatment.

The first

step

is to

select

the

proper

amine

to

use

in

each boiler.

Proper

application

of

the

amine

will

then

provide

a

larye

measure

of

protection

against

corrosion

in

condensate

return

systems.

6.

Point

of

contact.

At

FESA, contact

Nelson

Labbe,

commercial

7U3-664-5864,

AUTOVON

354-5864.

At

OCE, contact

Jerry

Kostos,

commercial

202-272-0586,

AUTOVON

285-U586.

FOR

THE

CHIEF

OF

ENGINEERS:

EDJWARD

T.

WATLING

Chief,

Facilities

Engineering

Division

Office

of

the Assistant

Chief of

Engineers

7/23/2019 A 168297

8/8

PROCUREMENT

DATA

FOR

DIRTHEILAKNIOTHAUC

A TRIBUTZ

RANME

TYPICAL

TEST

OF VALUES

VALUE

1VUOD

min.

max.

Form -

- liquid observe

Color APHA)

- 15 - Helig

Aquateste

Di

ethyl ami

noe thanol

by weight

99.5 -

-

Gas

Chromatog

Water,

by weight

- 0.2

- Carl

is her

Distillation Range, oC

ASTH

D107

Initial

158.0

-

Final

- 163.5

Specific Gravity

@

@

20/20 OC 0.88 0.89 ASTM D-87

Flash Point,

OF

125 Tagliabue

Closed

Cu

SViscosity

@20

0

C 3.5 cps

Brookfiel

Rotationr

Packaging

for

Shipment

Drums: Chemicals

NOIBN

Tank

Trucks:

Combustible Liquid, NOS;

NA1993

Tank

Cars: Combustible

Liquid,

NOS;

NA1993

Placarded Combustible;

STCC 4913186

Parcel

Post, Air Express,

Air

Freight

allowed.